Was the twentieth century warming mostly due to human emissions?

There has been no statistically significant warming for at least 15 years. Yet some people, like commentator “Michael the Realist”, who is currently trolling Joanne Nova’s blog, are claiming otherwise. His full claims are as follows

Again look at the following graph.

Now let me explain it to the nth degree.
# The long term trend over the whole period is obviously up.
# The long term trend has pauses and dips due to natural variations but the trend is unchanged.
# The current period is at the top of the trend.
# 2001 to 2010 is the hottest decade on the record despite a preponderance of natural cooling trends. (globally, ocean, land and both hemispheres)
# Hotter than the previous decade of 1991 to 2000 with its preponderance of natural warming events.
# Every decade bar one has been hotter than the previous decade since 1901.

Please explain why the above is true if not AGW with proof.

The claims against the warming standstill I will deal with in a later posting. Here I will look at whether the argument proves, beyond reasonable doubt, that AGW exists and is significant.

There might be a temperature series, but there is no data on greenhouse gases. There is data on the outcome, but there is no presentation of data on the alleged cause. It is like a prosecution conducting a murder trial with a dead body, with the cause of death not established, and no evidence presented linking the accused to the death. I will have to fill this bit in. The alleged cause of most of the twentieth century global warming is human greenhouse gas emissions. The primary greenhouse gas emission is CO2. First I will compare estimated global CO2 emissions with the warming trend. Second, I then show evidence that the twentieth century warming is nothing exceptional.

The relationship of CO2 emissions to average temperature is weak

Some time ago I downloaded estimates of national CO2 emissions data from what is now the CDIAC website, then in filled my own estimates for all major countries where there were data gaps, using the patterns of other countries and my knowledge of economic history. This shows steady growth up to 1945 (with dips in WW1, the Great Depression and at the end of WW2) The post war economic boom, the 1973 oil crisis, the recession of 1980-81 and the credit crunch of 2008 are clearly visible. It therefore seems reasonable and not too dissimilar from the increase in atmospheric CO2 levels.


I have charted the growth in human CO2 emissions against the HADCRUT3 data, putting them on a comparative scale. The 5 year moving average temperature increased by around 0.5oC between 1910 and 1944 and 0.6oC between 1977 and 2004. In the former period, estimated CO2 emissions increased from 0.8 to 1.4 giga tonnes. In the latter period, estimated CO2 emissions increased from 4.9 to 7.4 giga tonnes. The period in between the 5 year moving average temperature decreased very slightly and CO2 emissions increased from 1.4 to 4.9 giga tonnes. 1945 and the late 1998 have two things in common – the start of a stall in average surface temperature increases and an acceleration in the CO2 emission rate of increase. On the face of it, in so far as there is a relationship between CO2 emissions and temperature, it seems to be a pretty weak one.

The longer view

The case for claiming human emissions affect temperature is even weaker if you take a longer perspective. Human CO2 emissions were negligable before the industrial revolution, yet there is plenty of evidence that temperatures have shown larger fluctuations in last couple of millennia. Four example are Law Dome, Esper et al 2012, Gergis et al 2012 and the CO2 Science website.

This Law Dome ice cores are the highest quality ice cores in Antarctica.


There seems to be no warming there at all. With 75% of the global ice packs in Antarctica it is fortunate that there is nothing exceptional about Antarctica warming. But maybe the Arctic is different.

Esper et al 2012, published in Nature, has the following Summer temperature reconstruction for Northern Scandinavia over two millennia.


There is a twentieth century uptick, but only in the context of a long term cooling trend.

Focussing on the last 130 years shows something at odds with the global position.


The highest temperatures were in the 1930s, just like the record temperatures in the USA. The warming trend from the mid-1970s is still far greater than the global averages, but less than the warming trends in the early twentieth century. It corroborates data that shows recent warming trends are higher in the Arctic than the global average, but also shows claims that there is nothing significant in these trends.

I find the most convincing evidence is from the withdrawn Gergis 2012 temperature reconstruction for the combined land and oceanic region of Australasia (0°S-50°S, 110°E-180°E). This is because it set out with the aim of showing the opposite – that the recent warming was much more significant than anything in the last millennium. Despite breaking their own selection rules for proxies, they managed to only demonstrate that the last decade of the last millennium the warmest by the narrowest of margins. See below.


There are many reasons to reject the paper (see here), but one significant point can be illustrated. There were only three reconstructions had any data prior to 1430. There were two tree ring studies from New Zealand, and coral study from Palmyra Atoll. Plotting the decadal averages shows that the erratic Palmyra data suppresses the medieval period and exaggerates the late twentieth century warming. Further, Palmyra Atoll is over 2000 km outside the study area.


Finally, CO2Science.org specialises in accumulating evidence of the impacts of CO2. It also has a database of studies on the medieval warm period. There is a graph that summarizes the quantitative studies


Figure Description: The distribution, in 0.5°C increments, of Level 1 Studies that allow one

to identify the degree by which peak Medieval Warm Period temperatures either exceeded

(positive values, red) or fell short of (negative values, blue) peak Current Warm Period

temperatures.

In conclusion, on the face of it, there is very weak support for human emissions being the cause of most of the warming in the last century by the fact that changes in human emissions do not appear to move in line with changes in temperature. The case is further weakened by evidence that at times in the last 2000 years were warmer than in the current period. It does not discount the possibility that human emissions are responsible for some of the warming. But demonstrating that empirically would mean understanding and accurately measuring the full extent of the natural processes, then demonstrating that these were not operating as strongly as in previous epochs. By definition, the evidence will be more circumstantial than if there was a direct correlation. Furthermore, the larger the actual human impact the more circumstantial will be the evidence.

Esper et al 2012 Orbital forcing of tree-ring data – Corroborating the Sceptic Position

A new summer temperature reconstruction using of tree ring densities in Northern Scandinavia stir, raising some difficult questions for those who believe that C20th warming was caused by human activity

There are a couple of elements that corroborate sceptical beliefs that are not alluded to elsewhere.

Pointer to a low influence of CO2

There has been a decline in summer temperatures of 0.6 degrees.


From the abstract

Solar insolation changes, resulting from long-term oscillations of orbital configurations1, are an important driver of Holocene climate23. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m−2 net anthropogenic forcing since 1750

That is (From the supplementary information figure S13), a decline in temperatures of around 0.6 Celsius is due to a net reduction in orbital forcings of 6 W m−2.

From a 1998 article by Sherwood Idso* on climate sensitivities,

a total greenhouse warming of approximately 33.6°C sustained by a thermal radiative flux of approximately 348 W m–2

That is 6 W m−2 gives approximately 0.6 degrees temperature change. This implies 1.6 W m−2 gives approximately a 0.16 degree temperature change, so CO2 is not the largest influence on C20th warming.

Pointer to the global temperature adjustments being wrong

Yesterday I reblogged pieces of evidence by Steven Goddard indicating that the historical temperature record has been systematically manipulated. In particular, the inter-war warming has been reduced, whilst recent warming has been increased. From the paper, this abstract of the more recent warming trends.

Now compare with two versions of the Reykjavik mean temperatures to see which is closer. I know that Reykjavik is between 50 and 350 miles south of the area surveyed, but it does seem to corroborate one version over the other.

A possible alternative explanation to the lower late C20th temperatures  is in the comments at NoTricksZone. DirkH says

The line actually becomes unreliable from 1912 to the present as it is done with a “100 year spline filter” the paper says. Don’t give to much on the shape of the final wiggle. Can’t find any more information but obviously the window for the filter shrinks near the end, how will it react? Dunno…

Hu McCulloch ain’t too impressed: (2009)

http://climateaudit.org/2009/08/23/spline-smoothing/

*Joanna Nova has a summary here.

Gergis 2012 Mark 2 – Hurdles to overcome

BishopHill reported yesterday on the withdrawn Gergis paper that

The authors are currently reviewing the data and methods. The revised paper will be re-submitted to the Journal of Climate by the end of July and it will be sent out for peer review again.

It is worth listing the long list of criticisms that have been made of the paper. There are a lot of hurdles to overcome before Gergis et al 2012 should qualify for the status of a scientific paper.

My own, quite basic, points are:-

  1. Too few proxies for such a large area. Just 27 for > 5% of the globe.
  2. Even then, 6 are well outside the area.
  3. Of these six, Gergis’s table makes it appear 3 are inside the area. My analysis is below.


  4. Despite huge area, there are significant clusters – with massive differences between proxies at the same or nearby sites.
  5. There are no proxies from the sub-continental land mass of Australia.
  6. Need to remove the Palmyra Proxy because (a) it has errant readings (b) fails the ‘t’ test (c) > 2000km outside of the area, in the Northern Hemisphere.
  7. Without Palmyra the medieval period becomes the warmest of the millennium. But with just two tree ring proxies, one at 42 O South and the other at 43 O S representing an range from 0 to 50O S, this is hardly reliable. See the sum of proxies by year. Palmyra is the coral proxy in the 12th, 14th and 15th centuries.


On top of this are Steve McIntyre’s (with assistance from JeanS and RomanM) more fundamental criticisms:-

  1. The filtering method of Gergis excluded the high quality Law Dome series, but included the lower quality Vostok data, and the Oroko tree ring proxy. McIntyre notes that Jones and Mann 2003 rejected Oroko, but included Law Dome on different criteria.
  2. Gergis screening correlations were incorrectly calculated. JeanS calculated properly. Only 6 out of 27 proxies passed. (NB none of the six proxies outside the area passed)


  3. The Gergis initially screened 62 proxies. Given that the screening included proxies that should not have included 21 proxies, but should it have included some of the 35 excluded proxies. We do not know, as Gergis has refused to reveal these excluded proxies.
  4. Screening creates a bias in the results in favour of the desired result if that correlation is with a short period of the data. RomanM states the issues succinctly here. My, more colloquial take, is that if the proxies (to some extent) randomly show C20th warming or not, then you will accept proxies with a C20th uptick. If proxies show previous fluctuations (to some extent) randomly and (to some extent) independently of the C20th uptick, then those previous fluctuations will be understated. There only has to be a minor amount of randomness to show bias given that a major conclusion was

    The average reconstructed temperature anomaly in Australasia during A.D. 1238-1267, the warmest 30-year pre-instrumental period, is 0.09°C (±0.19°C) below 1961-1990 levels.

UPDATE 03/08/12

The end of July submissions date seems to have slipped to the end of September.

How Gergis Suppressed The Medieval Warm Period

The now withdrawn Gergis paper proudly proclaimed in the abstract

The average reconstructed temperature anomaly in Australasia during A.D. 1238-1267, the warmest 30-year pre-instrumental period, is 0.09°C (±0.19°C) below 1961-1990 levels.

On this basis, Gergis was able to say

A preliminary assessment of the roles of solar, volcanic, and anthropogenic forcings and natural ocean–atmosphere variability is performed using CSIRO Mk3L model simulations and independent palaeoclimate records. Solar and volcanic forcing does not have a marked influence on reconstructed Australasian temperature variations, which appear to be masked by internal variability.

This conclusion is from a single rogue proxy – the coral proxy from Palmyra Atoll.

There were only three temperature proxies covering this medieval peak period. Both Mt. Read in Tasmania and Oroko in New Zealand are tree ring proxies that cover the entire millennium. The Palymyra Atoll coral proxy data covers just 398 years over 4 periods. These are 1151-1221, 1319-1465, 1637-1704 and 1888-1999. Following Gergis, I have calculated the decadal averages. Below is the plot from my pivot table for the three proxies.


I contend that Palmyra is distinctly “odd” due to the following.

  1. Nowhere in the world am I aware of a single instance of massive cooling during the early 13th Century. If not rogue data, the it must be a purely local phenomena.
  2. Nowhere in the world am I aware of a single instance of massive cooling during the 17th Century. Nor was I aware the early 17th century had significant warm period. If not rogue data, it must be a purely local phenomena.
  3. The Hadcrut3 global temperature set has slight cooling at the end of the 19th century / start of the 20th Century, and a warming period from 1910 to 1940 almost as large as the warming period from 1975 to 1998. If not rogue data, it must be a purely local phenomena.
  4. The post 1960 warming trend is phenomenal. In fact it makes the twentieth century warming trend the largest of all the 27 proxies. (See table “Analysis of the Proxies in Gergis et al. 2012” below)

For these three reasons it would appear to be an outlier. So what is the impact?

I looked at the decadal average of the two tree-ring proxies and ranked the hundred decades from 1 for the highest to 100 for the lowest. I then took the decadal average of the three tree-ring proxies and similarly ranked the results.

The change is the decadal ranking was as follows:-


The medieval warm period is suppressed, and the twentieth century is “enhanced”.

Now let us be clear. There were 24 other proxies in the data set. However, none of the others were prior to 1430. Therefore the impact on the overall ranking will not be quite so marked. However, the fact remains that the conclusion that last decade of the 20th century is the warmest of the millennium is based on this one rogue data set.

But there are two more reasons that the Palmyra data set should not have been included in the reconstruction.

Firstly, the Gergis paper was withdrawn upon the publication of the JeanS ‘Gergis Significance’ t-values. Unsurprisingly, Palmyra was one of the proxies that failed the t-test, so is a rogue data set. See table below.

Secondly, is geography. The study is a “temperature reconstruction for the combined land and oceanic region of Australasia (0°S-50°S, 110°E-180°E)“. Palmyra Atoll is located at 5°52′ N, 162°06′ W, or over 2100Km (1300 miles) outside the study area.

Conclusion.

The Palmyra Atoll coral proxy study is clearly an outlier statistically and geographically. In no way can it be considered a suitable proxy for the Australasia region, yet the major, headline, conclusion of the Gergis et al 2012 temperature reconstruction relied upon it.


Mid-Pacific Coral temperature proxies from Gergis et al. 2012

How odd is the Palmyra Atoll Coral Proxy?

In the last post I noted that there was something odd about the Palmyra proxy used in the Gergis paper, particularly in the late 20th century. This is at 5°52′ N, 162°06′ W.

There are four other coral proxies in the Mid-Pacific area. There are two proxy studies from
Rarotonga in the Cook Islands at 21° 14′ 0″ S, 159° 47′ 0″ W and two from the Fiji. For all five proxies I calculated a nine year centred moving average.


Palmyra shows a late 20th century warming trend more than twice that of the other series. Unless there is a locally recorded temperature anomaly on the atoll, then this is clearly wrong. If there is a local temperature spike, then it one should question why it is included in a reconstruction for which it is over 2000km outside the boundary. Either way it should be deleted from the study.

So how reliable are coral proxies. Here we have two pairs. If they are a good proxy for temperature, then they should be a good proxy for each other. On Fiji, they studies be less than 150km apart and on Rarotonga less than 10km apart, meaning they should be near identical. So I have plotted the differences between the moving averages.


It is not a statistically sound method, but indicative of the real issues with the proxy data sets. It also seems that the further back, the greater the consistency. The Palmyra study has four sections, the oldest of which starts in the 12th Century. Although Gergis claims to have done a series of tests for robustness, there is no correlation test over the known temperature record. Given that a central conclusion is:-

The average reconstructed temperature anomaly in Australasia during A.D. 1238-1267, the warmest 30-year pre-instrumental period, is 0.09°C (±0.19°C) below 1961-1990 levels.

Given that there is some question of the selection of the ice core studies at Vostok in preference for the closer and more robust studies at Ice Dome, then central conclusion of the study is not credible on such a small number of proxies.

Palmyra Atoll Coral Proxy in Gergis et al 2012

There is a lot of discussion on Bishop Hill (here and here) and Climate Audit of a new paper in Journal of Climate “Evidence of unusual late 20th century warming from an Australasian temperature reconstruction spanning the last millennium“, with lead author, Dr Joëlle Gergis. The reconstruction was based upon 27 climate proxies, one of which was a coral proxy from Palmyra Atoll.

There are two issues with this study.

Location

The study is a “temperature reconstruction for the combined land and oceanic region of Australasia (0°S-50°S, 110°E-180°E)“. The study lists Palmyra Atoll as being at 6° S, 162° E, so within the study area. Wikipedia has the location at 5°52′ N, 162°06′ W, or over 2100Km (1300 miles) outside the study area. On a similar basis, Rarotunga in the Cook Islands (for which there are two separate coral proxy studies), is listed as being at 21° S, 160° E. Again well within the study area. Wikipedia has the location at 21° 14′ 0″ S, 159° 47′ 0″ W, or about 2000Km (1250 miles) outside the study area. The error has occurred due to a table with columns headed “Lon (°E)”, and “Lat (°S). Along with the two ice core studies from Vostok Station, Antarctica (Over 3100km, 1900 miles south of 50° S) there are 5 of the 27 proxies that are significantly outside the region.

Temperature Reconstruction

Palmyra Atoll reconstruction is one of just three reconstructions that has any data before 1430. From the abstract, a conclusion was

The average reconstructed temperature anomaly in Australasia during A.D. 1238-1267, the warmest 30-year pre-instrumental period, is 0.09°C (±0.19°C) below 1961-1990 levels.

From the proxy matrix I have plotted the data.


This indicates a massive change in late twentieth century temperatures, with 1996 being the most extreme on record.

The other two data sets with pre-1430 data are tree ring proxies from Mount Read, Tasmania and Oroko, New Zealand. These I have plotted with a 30 year moving average, with the data point at the last year.


There is something not right with the Palmyra Atoll proxy. The late 20th century trend is far too extreme. In the next posting I will compare to some other coral data sets.

Heartland Leak – The Implications

The stolen documents from the Heartland Institute have caused a lot of comment on the blogs. There are a number of things that will come out of this.

1. The consensus climate scientists and their cohorts cannot deal with numbers. Just as they have no sense of proportion with financial values (see Jo Nova on this), they likewise have no sense of proportion with sea level rise, temperature rise, or extreme weather events.

2. A better antonym of “sceptical” than “undoubting” or “believer” is “gullible”. Seems DeSmogBlog did not think to check out the authenticity of the damming 2012 strategy document, neither do they accept the Heartland rebuttal. It fitted the narrative, so they published within an hour of receiving the mail. Similarly The Guardian posted a number of one-sided reports (here, here, here), as did Roger Black of the BBC, without waiting to verify the facts. The most alarming 2012 strategy document is a fax (Judith Curry has other references)

3. A number of people, like me, will visit Heartland.org for the first time. They will find they have 7 policy areas employing 20 people, of which “Environment & Energy” employs 3. They specialise in providing cogent summaries of these issues to policy-makers. Whatever you think of their political stance, they are hardly the secretive, rabid backwoodsmen right-wingers that the alarmists project.

4. This support for spreading information in a concise, intelligible form also comes out in the sceptic-funding “exposes”. There is one-off support for Antony Watts who

proposes to create a new Web site devoted to accessing the new temperature data from NOAA’s web site and converting them into easy-to-understand graphs that can be easily found and understood by weathermen and the general interested public.” 

The, alleged, biggest recipient by far of monthly funding is Craig D Idso, who founded the co2science.org website. This provides summaries of climate science papers, collating their results to help give an overall picture of such as the medieval warm period, ocean acidification and the effect of CO2 on plant growth. For instance, I like this graphic summarising the proxy studies of the MWP showing that the Mannian Hockey Stick studies need to at least reconcile their claim that average global temperatures are warmer than in the last 1000 years.

5. It illustrates the upside-down nature of climatology, compared with conventional science. Conventional science is based on making bold statements and predictions that are substantiated by the evidence, with very clear and replicable methods. Over time it refines its techniques, strengthens its methods of analysis and sees its predictions confirmed. It does not need to denigrate, or attempt to silence its detractors. Like the historians of the holocaust, conventional science just points to the evidence and enlightens those who seek the truth. The real deniers of truth in history have been those who silence their opponents and fabricate distortions.

Overall, the leak exposes why the little Heartland Institute is so evil and dangerous to many. They threaten the jobs and reputations of tens of thousands of climate scientists, “policy-makers”, regulators, and powerful business interests in the alternatives to reliable energy. On the other hand, they are on the side of those made hungry by fuel crops competing with food, and of future generations globally, who will be worse-off by growth-sapping mitigation policies.

CAGW – Paralleling Kuhnian Science or New Labour Spin?

A review of Montford’s “Hockey Stick Illusion” suggests that it is an example science described by Thomas Kuhn in “The Structure of Scientific Revolutions”. Both the Hockey Stick in particular, and CAGW theory in general, I believe parallel something entirely different.

Catastrophic AGW theory is not an example of Kuhnian science. It was swallowed whole by the political establishment without going through the strictures of scientific acceptance. Furthermore, it is coupled with a major political policy objective - to constrain CO2 emissions. The IPCC was then set up to confirm and fortify the science and the policy. CAGW is thus not a proper science as such, but “politicised science”.

The Hockey Stick is the major example of this – a public relations ploy to promote policy and direct attention away from proper analysis of the data. The shenanigans may have milder and more short-lived parallels in other fields of science, but better parallels are to be found in New Labour Spin. That is, never admit to error; talk over opponents and view them as self-evidently wrong; deflect adverse comments by saying something different; deflect criticism and error by making an easily answerable point the major issue, or conceding a minor point; and then quickly moving the discussion onto safer ground. Most of all rely on image more than substance. In the case of CAGW, make peer review and agreement with collective experts the ultimate demarcations between science and non-science.

Interpreters of Interpreters to the nth degree

James Delingpole has attracted some ire for saying he is an “interpreter of interpreters”. I commented on Bishop Hill’s Blog

Wasn’t the original hockey stick paper an “interpreter of interpretations”? That is it gathered together a selection of data studies of past climate proxies and tried to give an interpretation – with some elements of bias. The IPCC, liking this paper’s conclusion then interpreted this as being definitive, despite its conclusions being contrary to many other studies. Learned societies, not least the Royal Society then interpret this as being the final argument, being the opinion of 2500 leading scientists. With learned pronouncements from the leading scientific organizations, the BBC, Guardian etc interprets that the science is settled, so the subject is closed. James Delingpole, in putting himself as a second tier interpreter, might be over-reaching himself in the ranking. However, he actually considers the arguments, unlike those who rely on multi-layered interpretations.

But more important than lowly a person is in the interpretation chain, is the reliability of that opinion compared with the ultimate reality that we are interpreting. Scientific enquiry must positively endeavour to free itself from biases. That was part of Popper’s injunction to make hypotheses capable of falsification. But with climate science

In the Hockey Stick Studies you will find (See “The Hockey Stick Illusion”)

  • Positive efforts to choose the limited number of data interpretations that suite the conclusion desired (with some having their own strong biases)
  • Giving these favourable studies an undue statistical bias against those that come to no, or contrary, conclusions.
  • Choosing the statistical tests that give favourable results.
  • A clique of people providing similar results through using similar methods around a core group of papers.
  • Peer review being used as a means of peer pressure in promoting favourable comments and papers, whilst obstructing contrary views.

The IPCC has been set up to act as a biased interpreter. It is there to argue the case for action on global warming climate change, not to arrive at a balanced opinion on the science.

The bias is upon interpretation in one direction is at every level of science and opinion.

  • Funding of research is based on conformity.
  • Pressure groups exist to “out” the non-conformists, like the McCarthyists of two generations ago.
  • There is also pressure on scientific organizations to declare unequivocal support.
  • There is severe censure and libelous statements made against any who dissent.

     

So, however much Delingpole may provide interpretations of interpretations without reading all the original literature, his opinions might be more valuable than those prestigious scientists who conform.


 

Copygate – the Underlying Significance

Steve McIntyre puts the Copygate scandal (paper here) of the 2006 Wegman Report into context.

A minor, but potentially significant, point in all of this is the timing issue. The Wegman Report was published in 2006. Given the Hockey Stick Team are keen to pick up on any points that may undermine any criticism of their scientific work, why has it taken four years to pick up on this accusation of plagiarism. I can see two possibilities.

  1. The climate consensus only reads what it wishes to read. Why would Bradley himself, who was cited in this very important report for paleo-climatology, did not have a quick read through it? Or at least a bright student who used his textbook and read around the subject a little.
  2. The hockey stick team is reeling at present. Montford’s Hockey Stick Illusion lays out clearly the debate, so “evidence” that may damage the reputation of the “opposition” is welcome.

Something that is perhaps related is why it took so long for anyone to ask for the data that underpinned MBH98. On the back of it Mann (and to a lesser extent, Bradley) received world-wide fame. Yet there was no upstart PhD student to take it apart, even when it overturned the established perception of there have been a medieval warm period.

This relates to a point I have made before on this blog. There seems to be a lack of critical and balanced analysis within climate science, coupled with the inability to compare and contrast the arguments.

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